Shelf unit



FIG. 1 is a front, top and right-side perspective view of a shelf unit showing my new design;

FIG. 2 is a rear, top and left-side perspective view thereof;

FIG. 3 is a front view thereof;

FIG. 4 is a rear view thereof;

FIG. 5 is a top view thereof;

FIG. 6 is a bottom view thereof; and,

FIG. 7 is a right-side view thereof; with the left-side view being a mirror image. 

CLAIM The ornamental design for a shelf unit, as shown and described. 